Cross-linked Poly Research Articles

Spider Silk-Inspired Binder Design for Flexible Lithium-Ion Battery with High Durability.

The development of flexible lithium-ion batteries (LIBs) imposes demands on energy density and high mechanical durability simultaneously. Due to the limited deformability of electrodes, as well as the flat and smooth surface of the metal current collectors, stable/durable/reliable contact between electrode materials and the current collectors remains a challenge, in particular, for electrodes with high loading mass and heavily deformed batteries. Binders play an essential role in binding particles of electrode materials and adhering them to current collectors. Herein, inspired by spider silk, a binder for flexible LIBs is developed, which equips a cross-linked supramolecular poly(urethane-urea) to the polyacrylic acid. The binder imparts super high elastic restorability originating from the meticulously engineered hydrogen-bonding segments as well as extraordinary adhesion. The developed binder provides excellent flexibility and intact electrode morphologies without disintegration even when the electrode is largely deformed, enabling a stable cycling and voltage output even when the batteries are put under tough dynamic deformation tests. The flexible LIBs exhibit a high energy density of 420WhL-1 , which is remarkably higher than reported numbers. The unique binder design is greatly promising and offers a valuable material solution for LIBs with high-loading mass and flexible designs.

Segmental dynamics of poly(tetrahydrofuran) cross-linked by click-chemistry: Single-chain nanoparticles vs cross-linked networks

Cross-linked poly(tetrahydrofuran) (PTHF) networks are useful as organic solvent/oil sorbents with high swelling capacity and mechanically robust solid polymer electrolyte membranes for lithium-ion batteries, as well as solid-state calcium ion batteries. Recently, the control of intra-vs intermolecular interactions has attracted significant interest to modulate the properties of dynamic networks involving non-covalent and dynamic covalent bonds. However, to the best of our knowledge, a comparison of the segmental dynamics in polymeric materials prepared exactly from the same precursor polymer through intra-vs intermolecular covalent bonds is still lacking. In this work, we report the dissimilar dynamic properties of PTHF-based materials prepared through intra-vs intermolecular click chemistry (i.e., films of PTHF-based single-chain nanoparticles (SCNPs) vs cross-linked networks). Particularly we observed remarkable similarities in the segmental relaxation time and glass transition temperature value but evident differences in the dynamic heterogeneities. These differences are attributed to the peculiar morphology of the intra-chain collapsed polymer chains (i.e., SCNPs).

Phytic acid mediated N, P co-doped hierarchical porous carbon with boosting capacitive storage for dual carbon lithium-ion capacitor

Lithium-ion capacitors (LICs) merged the energy characteristic of lithium-ion batteries and power characteristic of supercapacitors have aroused intensive attention. Nevertheless, the low capacity of capacitor-type cathode confines the development of LICs. Herein, an economic and efficient approach is developed to fabricate nitrogen and phosphorus co-doped hierarchical porous carbon (NP-HPC) by carbonizing cross-linked phytic acid and poly pyrrole/aniline precursor (PACP), in which phytic acid acts not only as a chemical crosslinker to regulate the precursor structure, but also a phosphorus source for dopant, thus providing more active sites for Li storage and enhancing structural stability. As-prepared NP-HPC cathode with enlarged specific surface area (∼2750 m2 g−1) and more micropores (∼1.410 nm) delivered a high specific capacity of 89 mAh g−1, with an ultrahigh capacity retention of 88.6% after 10000 cycles at 1.0 A g−1. DFT calculations demonstrated the co-dopant of N and P atoms synergistically improve the Li+ adsorption energy and electrochemical stability. More importantly, the assembled dual carbon LICs employing homologous NP-HPC and N, P co-doped spherical carbon (NP-SC) electrodes from the same precursor exhibit a maximum energy density of 121 Wh kg−1 at a power density of 92 W kg−1, with long-term cycling stability over 3000 cycles at 1 A g−1 with 80.2% retention.

Chemically and Physically Cross-Linked Inorganic–Polymer Hybrid Solvent-Free Electrolytes

Safe, self-standing, all-solid-state batteries with improved solid electrolytes that have adequate mechanical strength, ionic conductivity, and electrochemical stability are strongly desired. Hybrid electrolytes comprising flexible polymers and highly conductive inorganic electrolytes must be compatible with soft thin films with high ionic conductivity. Herein, we propose a new type of solid electrolyte hybrid comprising a glass–ceramic inorganic electrolyte powder (Li1+x+yAlxTi2−xSiyP3−yO12; LICGC) in a poly(ethylene)oxide (PEO)-based polymer electrolyte that prevents decreases in ionic conductivity caused by grain boundary resistance. We investigated the cross-linking processes taking place in hybrid electrolytes. We also prepared chemically cross-linked PEO/LICGC and physically cross-linked poly(norbornene)/LICGC electrolytes, and evaluated them using thermal and electrochemical analyses, respectively. All of the obtained electrolyte systems were provided with homogenous, white, flexible, and self-standing thin films. The main ionic conductive phase changed from the polymer to the inorganic electrolyte at low temperatures (close to the glass transition temperature) as the LICGC concentration increased, and the Li+ ion transport number also improved. Cyclic voltammetry using [Li metal|Ni] cells revealed that Li was reversibly deposited/dissolved in the prepared hybrid electrolytes, which are expected to be used as new Li+-conductive solid electrolyte systems.

One-Pot Preparation of Skin-Inspired Multifunctional Hybrid Hydrogel with Robust Wound Healing Capacity.

Bioinspired hydrogels have demonstrated multiple superiorities over traditional wound dressings for wound healing applications. However, the fabrication of bioinspired hydrogel-based wound dressings with desired functionalities always requires multiple successive steps, time-consuming processes, and/or sophisticated protocols, plaguing their clinical applications. Here, a facile one-pot strategy is developed to prepare a skin-inspired multifunctional hydrogel within 30 min by incorporating elastin (an essential functional component of the dermal extracellular matrix), tannic acid, and chitosan into the covalently cross-linked poly(acrylamide) network through noncovalent interactions. The resulting hydrogel exhibits a Young's modulus (ca. 36 kPa) comparable to that of human skin, a high elongation-at-break (ca. 1550%), a satisfactory tensile strength (ca. 61 kPa), and excellent elastic self-restorability, enabling the hydrogel to synchronously and conformally deform with human skin when used as wound dressings. Importantly, the hydrogel displays a self-adhesive property to skin tissues with an appropriate bonding strength (ca. 55 kPa measured on intact porcine skin), endowing the hydrogel with the ability to rapidly self-adhere to intact human skin, sealing the wound surface and also easily being removed without residue left or trauma caused to the skin. The hydrogel also possesses remarkable antibacterial activity, antioxidant capability, and hemocompatibility. All of these collective beneficial properties enable the hydrogel to significantly accelerate the wound healing process, outperforming the commercial wound dressings.

UV-Induced Thiol-Ene "Click" Surface Grafting Polymerization on BOPP Substrate and Its Postmodifying for Hydrophilic and Antibacterial Applications.

This paper proposed a novel and versatile surface modification route by integrating UV light-mediated thiol-ene "click" surface grafting polymerization and postmodification via the reactions of the surface thiol groups. At first, poly(thiol ether) layers with tunable thiol group density, up to 8.2 × 102 ea/nm3 for cross-linked grafting layers, were grafted from biaxially oriented polypropylene (BOPP) film. Then, the surface -SH groups reacted with epoxy compounds to introduce quaternary ammonium salt. With the immobilized quaternary ammonium salt and coordinated Zn2+ ions, the modified film demonstrated 99.98% antibacterial rate against Staphylococcus aureusafter soaking in DI water for 21 days and in a highly alkaline environment (0.1 M NaOH aqueous solution) for 3 days, and the surface water contact angle decreased to 39°. At last, the polymethacrylate chains were also successfully grafted from the surface thiol groups of the cross-linked poly(thiol ether) under visible light irradiation. With 2-(dimethyldodecylammonium) ethyl methacrylate as the grafting monomer, the modified BOPP film had shown a 99.99% antibacterial rate against both Escherichia coliand S. aureus. Meanwhile, with 2-methacryloxyethyl phosphoryl choline as grafting monomer, the modified surface showed an excellent antibioadhesion of living S. aureus, and the surface water contact angle was as low as 48°.

Indirect method for preparing dual crosslinked eutectogels with high strength, stretchability, conductivity and rapid self-recovery capability as flexible and freeze-resistant strain sensors

The growing demand for stretchable conductor materials in flexible electronic technologies has led to increased focus on developing conductive gels. However, existing hydrogels have poor temperature resistance, and ionogels may have potential toxicity, limiting their use in bio-related applications. This work focuses on the development of the emerging eutectogels with both mechanical and electrical properties, which have traditionally been challenging to achieve. We present an indirect method to prepare dual crosslinked eutectogels that possess high strength, stretchability, conductivity and rapid self-recovery capability. The approach involves using water molecules as a co-solvent to form a deep eutectic solvent through a three-step process, followed by ionically cross-linking poly(acrylamide-co-acrylic acid) with Fe3+. The resulting eutectogels have a balanced mechanical strength with a tensile strength up to 6.17 MPa, large stretchability up to 1067%, a modulus of 1.25 MPa, and excellent toughness of 20.95 MJ/m3. In addition, the eutectogels exhibit high ionic conductivity of 10.29 mS/cm, rapid self-recovery and low temperature tolerance capability (up to −50 °C). To our knowledge, the eutectogels with balanced tensile strength, toughness, conductivity, and low-temperature tolerance can hardly be achieved. Moreover, the conductive eutectogel also exhibit high sensitivity with a gauge factor of 9.47 at strain of 700% with fast response time, making them promising candidates for soft human-motion sensors that can accurately detect human motions with high sensitivity and good durability over a wide temperature range. The findings provide new insights into developing eutectogels with both mechanical and electrical properties, opening opportunities in flexible electronics, soft robotics, and energy storage devices.

Bioinspired Integrated Auxetic Elastomers Constructed by a Dual Dynamic Interfacial Healing Strategy.

Auxetic materials are appealing due to their unique characteristics of transverse expansion while being axially stretched. Nevertheless, current auxetic materials are often produced by the introduction of diverse geometric structures through cutting or other pore-making processes, which heavily weaken their mechanical performance. Inspired by the skeleton-matrix structures in natural organisms, this study reports an integrated auxetic elastomer (IAE) composed of high-modulus cross-linked poly(urethane-urea) as a skeleton and low-modulus non-cross-linked poly(urethane-urea) as a complementary-shape matrix. Benefiting from disulfide bonds and hydrogen-bond-promoted dual dynamic interfacial healing, the resulting IAE is flat, void-free, and has no sharp soft-to-hard interface. Its fracture strength and elongation at the break are increased to 400% and 150%, respectively, of the values of corrugated re-entrant skeleton alone, while the negative Poisson's ratio (NPR) reserves within a strain range of 0%-104%. In addition, the advantageous mechanical and auxetic properties of this elastomer are further confirmed by finite element analysis. The concept of combining two dissimilar polymers into an integrated hybrid material solves the problem of the deterioration in mechanical performance of auxetic materials after subtractive manufacturing, while preserves the NPR effect in a large deformation, which provides a promising approach to robust auxetic materials for engineering applications.

Facile Approach for the Preparation of Robust and Thermally Stable Silyl Ether Cross-Linked Poly(ethylene-vinyl acetate) Vitrimers

Facile Approach for the Preparation of Robust and Thermally Stable Silyl Ether Cross-Linked Poly(ethylene-vinyl acetate) Vitrimers

Nanoscale iodophoric poly(vinyl amide) coatings for the complexation and release of iodine for antimicrobial surfaces

Wound infection exacerbated by multidrug-resistant (MDR) bacteria has necessitated the need for wound dressing materials with embedded antimicrobial property to prevent the development of chronic wounds. Iodine (I2), typically as a poly(vinyl pyrrolidone)-I2 (PVP–I) complex, is a widely used antiseptic agent in wound care owing to its efficacy, safety, and low probability to cause further resistance. Despite extensive research on PVP–I formulations, there is potentially a large selection of poly(vinyl amide)s that have remained largely unexplored as iodophoric materials, particularly as coatings for wound dressings and medical devices. Therefore, in this study we prepared a series of stable, cross-linked poly(vinyl amide) coatings via plasma polymerization and studied their structure–property relationships for the complexation and release of I2. Plasma polymerized poly(N-vinyl-2-pyrrolidone) (pPVP), poly(N-methyl-N-vinylacetamide) (pPMVA) and poly(N-vinylcaprolactam) (pPVCl) nanoscale coatings were prepared with uniform thicknesses of 330–340 nm and low surface roughness. Complexation of I2 as polyiodides resulted in a significant increase in the pPVCl coating thickness in phosphate buffered saline (PBS), consistent with the Hofmeister effect. Raman spectroscopy confirmed that the I2 was complexed exclusively as the triiodide ion (I3-) in all coatings, which was confirmed by synchrotron X-ray photoelectron spectroscopy (XPS) experiments. Nuclear magnetic resonance (NMR) spectroscopy of poly(vinyl amides) was employed to further prove that the complexing species was hydrogen triiodide (HI3). The loading of I2 species increased from pPVP < pPMVA < pPVCl, with percentage elemental compositions of 1.3, 1.8, and 2.9%, respectively, which correlated with the extent of nitrogen loss during polymerization and oxidation, and was also in agreement with determined negative zeta potential values. However, quantification of the released I2 species over 5 h showed that the greatest release was observed from pPMVA (121.3 µg.cm−2), with pPVP (77.4 µg.cm−2) and pPVCl (74.6 µg.cm−2) releasing a similar amount, highlighting that I2 release from poly(vinyl amide) coatings is a function of the loading and composition of the polymer, not just the I2 complexing amide motif. The I2 complexed pPMVA coated wound dressings were highly effective against Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus, the two major strains associated with wound infection, reducing bacterial viability by up to 4 and 7 (log10 reduction) orders of magnitude. Overall, the poly(vinyl amide) coatings are promising iodophors for the prevention and treatment of wound infections.

Development of Jeffamine cross-linked poly(vinyl chloride) films by sequential CuAAC click chemistry and aza-Michael addition

The objective of this study is to present a promising route to design a series of new poly(vinyl chloride) (PVC) films cross-linked with polyetheramine (PEA), namely jeffamine, by combining copper (I)-catalyzed azide-alkyne cycloaddition “click” reaction (CuAAC) and aza-Michael addition (PVC-Jeffs). In the first step, the clickable azido‐functional PVC is prepared easily by displacement reaction between chlorine groups and sodium azide (PVC-N3) and then reacted with propargyl acrylate by CuAAC (PVC-acr). The second step is aza-Michael addition of PVC-acr and Jeffamine to achieve the desired PVC-Jeffs. Transparent and uniform films are prepared by casting from dichloromethane solvent. The effect of loading ratio by weight (PVC/Jeffamine (w/w) = 9:1; 8:2 and 7:3) on the thermal properties of final PVC-Jeffs is systematically explored. The chemical structure of PVC-Jeffs and their intermediates is characterized by Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (1H-NMR) spectroscopies, whereas thermal characteristics of the samples are investigated by thermogravimetric (TGA) and differential scanning calorimetry (DSC) analyses. The higher Jeffamine loaded PVC-Jeff exhibit enhanced thermostability and glass transition temperature with the T g of 69.9 °C. Hence, this kind of strategy to achieve the PVC based films with good characteristics is expected to be applied in the preparation of biomedical materials.

Versatile Biodegradable Poly(acrylic acid)-Based Hydrogels Infiltrated in Porous Titanium Implants to Improve the Biofunctional Performance.

This research work proposes a synergistic approach to improve implants' performance through the use of porous Ti substrates to reduce the mismatch between Young's modulus of Ti (around 110 GPa) and the cortical bone (20-25 GPa), and the application of a biodegradable, acrylic acid-based polymeric coating to reduce bacterial adhesion and proliferation, and to enhance osseointegration. First, porous commercially pure Ti substrates with different porosities and pore size distributions were fabricated by using space-holder techniques to obtain substrates with improved tribomechanical behavior. On the other hand, a new diacrylate cross-linker containing a reduction-sensitive disulfide bond was synthesized to prepare biodegradable poly(acrylic acid)-based hydrogels with 1, 2, and 4% cross-linker. Finally, after the required characterization, both strategies were implemented, and the combination of 4% cross-linked poly(acrylic acid)-based hydrogel infiltrated in 30 vol % porosity, 100-200 μm average pore size, was revealed as an outstanding choice for enhancing implant performance.

Guard Cell-Inspired Ion Channels: Harnessing the Photomechanical Effect via Supramolecular Assembly of Cross-Linked Azobenzene/Polymers.

Stimuli-responsive ion nanochannels have attracted considerable attention in various fields because of their remote controllability of ionic transportation. For photoresponsive ion nanochannels, however, achieving precise regulation of ion conductivity is still challenging, primarily due to the difficulty of programmable structural changes in confined environments. Moreover, the relationship between noncontact photo-stimulation in nanoscale and light-induced ion conductivity has not been well understood. In this work, a versatile design for fabricating guard cell-inspired photoswitchable ion channels is presented by infiltrating azobenzene-cross-linked polymer (AAZO-PDAC) into nanoporous anodic aluminum oxide (AAO) membranes. The azobenzene-cross-linked polymer is formed by azobenzene chromophore (AAZO)-cross-linked poly(diallyldimethylammonium chloride) (PDAC) with electrostatic interactions. Under UV irradiation, the trans-AAZO isomerizes to the cis-AAZO, causing the volume compression of the polymer network, whereas, in darkness, the cis-AAZO reverts to the trans-AAZO, leading to the recovery of the structure. Consequently, the resultant nanopore sizes can be manipulated by the photomechanical effect of the AAZO-PDAC polymers. By adding ionic liquids, the ion conductivity of the light-driven ion nanochannels can be controlled with good repeatability and fast responses (within seconds) in multiple cycles. The ion channels have promising potential in the applications of biomimetic materials, sensors, and biomedical sciences.

In vitro enzymatic degradation of the PTMC/cross-linked PEGDA blends.

Introduction: Poly(1,3-trimethylene carbonate) (PTMC) is a flexible amorphous polymer with good degradability and biocompatibility. The degradation of PTMC is critical for its application as a degradable polymer, more convenient and easy-to-control cross-linking strategies for preparing PTMC are required. Methods: The blends of poly(trimethylene carbonate) (PTMC) and cross-linked poly(ethylene glycol) diacrylate (PEGDA) were prepared by mixing photoactive PEGDA and PTMC and subsequently photopolymerizing the mixture with uv light. The physical properties and in vitro enzymatic degradation of the resultant PTMC/cross-linked PEGDA blends were investigated. Results: The results showed that the gel fraction of PTMC/cross-linked PEGDA blends increased while the swelling degree decreased with the content of PEGDA dosage. The results of in vitro enzymatic degradation confirmed that the degradation of PTMC/cross-linked PEGDA blends in the lipase solution occurred under the surface erosion mechanism, and the introduction of the uv cross-linked PEGDA significantly improved the resistance to lipase erosion of PTMC; the higher the cross-linking degree, the lower the mass loss. Discussion: The results indicated that the blends/cross-linking via PEGDA is a simple and effective strategy to tailor the degradation rate of PTMC.

UV-Controlled Nitrene Crosslinking in Poly(phenylene oxide) Anion Exchange Membranes

Anion exchange membranes (AEMs) promise significant capital cost saving associated with enabling use of Pt-group-free electrodes and components in alkaline fuel cells and electrolyzer devices. However, AEMs often lack the chemical and mechanical stability required for widespread commercial adoption. Crosslinking has proven to be an effective method to permit increased ion exchange capacity (IEC) while preventing exponential water uptake and retaining both conductivity and mechanical strength. In this work, we leverage molecular dynamics simulations to explore crosslinking methodologies in silico. We present a reproducible and quantitative UV-based nitrene chemistry that utilizes a mobile crosslinker that is straightforward to synthesize and implement. This crosslinking strategy significantly mitigates excess water uptake and improves alkaline stability without sacrificing IEC during the cure process. Additionally, we characterize electrochemically fielded AEMs by small angle X-ray scattering, mechanical strength testing, and other post-mortem analyses. The operational lifetime of crosslinked AEMs prepared in this work is 5 times greater than corresponding untreated AEMs.This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 within the LDRD program 21-ERD-013. LLNL-ABS-848147.

High Performance Anode-Free Lithium Pouch Cells Employing Lithiophilic Gel Polymer Electrolyte with Ion Conductive Network

Anode-free lithium metal batteries have recently emerged as a next generation battery due to increased energy density by adopting bare current collector as an anode without excess lithium source. However, lithium tends to grow in uncontrolled dendritic form when depositied on a heterogeneous current collector, which eventually leads to low coloumbic efficiency and poor life span of the battery. Recent studies have attempted to apply artificial solid electrolyte interphase (SEI) on the current collector to solve theses problems. PEO-based polymeric artificial SEI is commonly used due to high lithium ion conductivity and flexiblility, but its weak physical properties limit its practical application. Herein, we report a chemically cross-linked poly (ethylene glycol) diacrylate (PEGDA)-based gel polymer electrolyte containing AgNO3 as Li nucleation seed for uniform Li deposition. It guides uniform Li-ion flux at the electrode/electrolyte interface and provides mechanical strength to suppress lithium dendrite growth. The gel polymer electrolyte was applied to anode free pouch cell and its cycling performance was investigated in the voltage range of 3.6 - 4.3 V at 0.5 C rate. Our results demonstrate that the proper combination of electrolyte and current collector can increase the conversion of polymerization and achieve stable interfacial properties with electrodes, resulting in improvement of the cycle life of anode free lithium pouch cell.

Preparation of elastic hydrogel films via in-situ ketalization of Poly(vinyl alcohol) and ZnO nanoparticle doped Poly(vinyl ketal) films as antibacterial surface

Cross-linked and flexible poly(vinyl acetone ketal) (PV-A-K) films have been prepared as a result of ketalization reaction and monolith formation of poly(vinyl alcohol) (PVA), which has the feature of forming films quickly and is frequently used in biological fields. In this novel method, flexible PV-A-K films have been produced simply and in a short time accompanied by monolith formation without any catalyst in acetone. The effect of acetone ratio on the physical properties (i.e., swelling and mechanical properties) of such formations has been investigated to reveal significant influences of it. In addition, zinc oxide (ZnO) nanoparticles synthesized via the solvothermal method have been doped into PV-A-K films during film preparation. The prepared PV-A-K and ZnO doped PV-A-K films have been characterized with SEM, XRD, and FT-IR. Their mechanical properties have been investigated with a universal mechanical test machine. The acetone ratio is quite effective both on the porosity and stress/strain properties of the films. Antibacterial activities of the films are evaluated against four different strains (E. coli, S. aureus, P. aeruginosa, and E. faecalis) via the disk diffusion method. The films are selectively effective against S. aureus. These highly flexible and elastic films have great potential for biomedical applications, wound dressing, and antibacterial surface preparation.

Nano-CeO2-Loaded Polyzwitterionic Double-Network High-Strength Hydrogel for Highly Enhanced Synergistic Marine Antifouling.

Although many antibiofouling materials have been developed based on either bacterial-killing or antiadhesion effects, the integration of both the effects in one material remains challenging for achieving highly enhanced synergistic antibiofouling. In this study, we have explored a nano-CeO2-loaded double-network hydrogel by introducing CeO2 nanorods into a polyzwitterionic hydrogel via a simple one-pot method for achieving highly efficient antifouling. First, the CeO2 nanorods dispersed in the hydrogel, as an outstanding nanozyme, have highly efficient bacterial-killing performance. Second, the superhydrophilic polyzwitterionic hydrogel provides a dense hydrated layer on the surface and subsequently excellent broad-spectrum antiadhesion behavior. Most importantly, the bacterial killing and antiadhesion of this hydrogel can work synergistically to largely improve the marine-antifouling performance. Moreover, the double-network structure of this hydrogel, including the covalently cross-linked polyzwitterion hard network and the physically cross-linked poly(vinyl alcohol) soft network, can provide greatly improved mechanical properties (2.44 MPa of tensile strength reaches and 21.87 MPa of compressive strength). As a result, among the existing marine-antifouling hydrogels, the CeO2-loaded polyzwitterionic double-network hydrogel can achieve outstanding antifouling performance, which can sustain for over 6 months in a real marine environment. This work provides a promising marine-antifouling hydrogel, which will also inspire antifouling research of a new strategy and materials.

Phosphoric acid-doped cross-linked poly(phenylene oxide)-based membranes for high temperature proton exchange membrane fuel cells

In this study, a series of cross-linked poly (phenylene oxide) (PPO)-based membranes with and without rotatable ethylene oxide spacers are prepared. Both PPO-based membranes possess good thermal stability, excellent oxidative stability, and satisfactory dimensional stability in phosphoric acid (PA) owing to their cross-linked structure and PPO backbone. The cross-linked PPO-based membrane with a rotatable ethylene oxide spacer exhibits enhanced conductivity, higher tensile strength, and better oxidative stability compared with that without the rotatable spacer. Owing to a better trade-off effect, the cross-linked membrane with the rotatable ethylene spacer exhibits higher H2/air cell performance (maximum power density, 237 mW cm−2) than that without the rotatable spacer (maximum power density, 144 mW cm−2). The introduction of rotatable spacers is an effective method for enhancing the performance of high-temperature proton exchange membranes.

Dual Cross-Linked Poly(vinyl alcohol)-Based Anion Exchange Membranes with High Ion Selectivity for Vanadium Flow Batteries

Dual Cross-Linked Poly(vinyl alcohol)-Based Anion Exchange Membranes with High Ion Selectivity for Vanadium Flow Batteries